Studies continue in an effort to develop new and better biologic markers for cancer. For those under evaluation, application has been and will continue to be made to specific clinical studies for consideration as to the eventual place each potential marker may have in the treatment of cancer. Investigations include specific protocol studies involving (1) patients with chemotherapy responsive disease undergoing experimental therapy, particularly breast cancer, (2) patients following surgery for cancer and (3) patients in remission following chemotherapy or radiotherapy. Ongoing evaluations include carcino-embryonic antigen, human chorionic gonadotropin, tRNA nucleosides, polyamines, beta-aminoisobutyric acid, urinary hydroxy proline, serum protein bound carbohydrates and specific serum enzymes as possible sensitive indicators of metastic tumor involvement of the liver.